The present invention pertains to an electrochemical gas sensor with at least two electrodes and an electrolyte in a sensor housing with an opening for the entry of the measured gas and also relates to a method of forming an electrochemical gas sensor.
An electrochemical gas sensor of this class is shown, e.g., in DE 198 45 318 C2. In all such prior-art gas sensors, the electrodes used are introduced into a sensor housing separately and individually, and are contacted by means of suitable wires or pins, and the electric contacts are led out through the sensor housing. The electrodes are arranged stacked at spaced locations from one another. Separators in the form of, e.g., porous, electrolyte-impregnated glass mats are used for this purpose, so that no electric short-circuit can develop between the electrodes. These prior-art electrochemical gas sensors require a great, predominantly manual effort for their assembly, which is, moreover, complicated and may lead to errors.
WO 98/25 138 shows the stacked design of a plurality of fuel cells. Each individual fuel cell has separate supply lines for two different gases, which are located above and below the optionally folded electrode array limited by gas-permeable membranes.
The object of the present invention is to provide a simple electrochemical gas sensor that can be assembled in a few steps.
According to the invention, an electrochemical gas sensor is provided with at least two electrodes and an electrolyte in a sensor housing with an opening for the entry of the measured gas. The electrodes with the associated electric lines are applied in a planiform manner on a gas-permeable membrane strip that is impermeable to the electrolyte. The membrane strip is deposited in the sensor housing in a zigzag-folded pattern, so that the membrane strip limits the opening of the sensor housing for the entry of the measured gas. The electrodes are arranged stacked at spaced locations from one another in the sensor housing due to the membrane strip deposited in a zigzag-folded pattern.
An essential advantage of the present invention arises especially from the fact that the membrane strip, which accommodates the electrodes and their electric lines and is impermeable to the electrolyte and permeable to gases, is manufactured in an automated manner at low cost, so that the complicated and time-consuming assembly of the individual components, which has hitherto been usual, is eliminated. The electrodes and their electric lines are preferably printed or sintered, sputtered or vapor-deposited on the membrane strip continuously in an operation preceding the assembly of the sensor housing. The membrane strip is subsequently separated section by section, so that each membrane strip section has the electrodes and electric lines intended for one gas sensor.
The electrodes with their associated electric lines are applied in a planiform manner on the membrane strip at spaced locations on one side in the longitudinal direction of the membrane strip and optionally additionally in a laterally offset pattern such that the membrane strip, deposited in the sensor housing folded in a zigzag pattern, brings about the electrical separation of the electrodes.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.